For a nuclear war, just hold the potato outside and let the nuke take care of the rest. As for a zombie invasion, who's going to have time to eat a potato when you're running from zombies 24/7.
Oh yeah... I guess the nuke could cook the potato for you, good point , zack :) but I think you might want to have a tasty prepared potato to offer to the zombies to distract them from eating your brain? Might work.
Definitely do not cook it. I'd freeze up a bunch of raw ones to load up in my VampireZombie Bazooka. It's the only thing that works, trust me. I speak from experience. That, and scotch tape of course.